1. Field of the Invention
The present invention relates to a multiplexer or demultiplexer optical component and, in particular, to a multiplexer or demultiplexer for a wavelength division multiplexed optical system.
2. Discussion of Related Art
Wavelength division multiplexing has become a standard in optical networks over the last few decades. Wavelength division multiplexing (WDM) exploits the potential bandwidth of optical fibers by transmitting data over several channels on the same fiber. Each channel is transmitted on the optical fiber at a different wavelength. The rate of data transmission over the fiber, then, can be increased by a factor of M, where M is the number of channels (i.e., the number of different wavelengths) being transmitted over the fiber.
Recently, an explosion of WDM technologies has appeared on the market. Systems having 8, 16, and 32 channels have become commonplace. Dense WDM, DWDM, for example, can have 32 channels following an ITU grid with 0.8 nm wavelength separation. However, in order to effectively utilize the bandwidth of the optical fiber, optical signals must be multiplexed and demultiplexed onto the fiber.
In WDM systems, optical signals are transmitted over a set of M channels. The M channels are multiplexed at the transmitter so that M wavelengths of light are simultaneously transmitted on an optical fiber to a receiver system. At the receiver system, the M channels are demultiplexed into optical signals transmitted at individual wavelengths of light. The individual wavelengths of light can then be directed to photodetectors so that the optical signals can be converted into electrical signals for processing by subsequent electronic circuitry.
In some demultiplexing systems, an optical fiber can be directly attached to a dielectric waveguide. The waveguide geometry exploits interference and/or diffraction in order to separate different wavelength constituents of the input light beam. These systems are difficult to fabricate, have large insertion losses, and are only applicable to single-mode fibers.
Demultiplexing can be accomplished with diffraction gratings, prisms, or filters, for example. The major problem with such devices is that they often include bulky and costly lenses and such which are very hard to reliably align, leading to large manufacturing costs and a bulky final product. Conventionally, most WDM or DWDM demultiplexer systems include filter-based demultiplexers, primarily do to the fact that formation of gratings in glass are more expensive to fabricate than are filters.
In the past few years, with the advent of high data rate communications, the concept of wide WDM (WWDM) (channel spacings of ˜25 nm) has been proposed and is currently being actively considered as a standard for 10 Gigabit Ethernet and Fiber Channel communication systems. Currently, demultiplexer systems being proposed for use in WWDM systems have involved filter based demultiplexer systems. However, filter based demultiplexer systems are expensive, primarily because of the assembly costs due to the small filters and multiple other components which require time consuming alignment and assembly. Furthermore, the design of a filter based demultiplexer system is not scalable to systems having more channels. Also, the design of the filter based systems cannot be scaled down to small physical beam separation distances due to limitation on the size of filters and beam clipping. Finally, filter based demultiplexer systems require complicated alignment of several subassemblies.
Therefore, there is a need for a less expensive and more versatile demultiplexer system for utilization in WWDM, WDM or DWDM systems.